HF Cat vs Test pipes on my new Z

Jordo!

For max power and minimal rasp you will want resonated test pipes, ideally with long, L or J shaped bung extenders for the secondary O2's.

You may still require a tune to turn off the associated CEL if the ECU sees the primary and secondary O2's matching voltage change rates too closely.

Really, any set will do. If you don't care about rasp or rattle (it is bad, tho'), a set of unresonated TP's from ebay will serve just fine.

That said, if you get TP's, I would consider investing in a tune anyway to improve throttle response, clean up AFR's, and bump up ignition advance.

Or, if you have the coin and either the tools or a shop willing to do it, skip the TP's and go for Long tube headers (and a tune). I recommend PPE.

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